| EFL | effective focal length |
|---|---|
| FCD | feces collection device; fibrocystic disease; fibrocystic dysplasia; focal cytoplasmic degradation |
| FD | familial dysautonomia; family doctor; fan douche; fatal dose; fetal danger; fibrin derivative; fibro... |
| FDH | familial dysalbuminemic hyperthyroxinemia; focal dermal hypoplasia; formaldehyde dehydrogenase |
| FEH | focal epithelial hyperplasia |
| Kohler illumination | <technique> The recommended type of optical microscope illumination in which the image of the lamp filament is focussed in the lower focal plane of the substage condenser. As opposed to collimated illumination in which the light emitting surface is imaged in the object. Collimated illumination requires even intensity across the light emitting surface but is preferable for certain types of microscopy. Kohler illumination gives even illumination on the object even if there are irregularities in the brightness of the light emitting surface. (18 Nov 1997) |
|---|---|
| lateral illumination | Illumination in which a beam of light is directed diagonally to an object so that it is brilliantly illuminated while the surrounding area is in shadow. Synonym: lateral illumination, oblique illumination. Kohler illumination, a method of illumination of microscopic objects in which the image of the light source is focused on the substage condenser diaphragm and the diaphragm of the light source is focused in the same plane with the object to be observed; maximises both the brightness and uniformity of the illuminated field. (05 Mar 2000) |
| anterior focal point | The point where parallel rays from the retina are focused. (05 Mar 2000) |
| back focal length | <microscopy> As measured on the principal axis, from the second lens vertex to the back focal point of the lens. It is not the equivalent of the focal length. (05 Aug 1998) |
| back focal plane | <microscopy> The plane, normal to the lens axis, situated at the back focus of a lens. (05 Aug 1998) |
| Berger's focal glomerulonephritis | Glomerulonephritis affecting a small proportion of renal glomeruli which commonly presents with haematuria and may be associated with acute upper respiratory infection in young males, not usually due to streptococci; associated with IgA deposits in the glomerular mesangium and may also be associated with systemic disease, as in Henoch-Schonlein purpura. Synonym: Berger's disease, Berger's focal glomerulonephritis, focal nephritis, IgA nephropathy. (05 Mar 2000) |
| glomerulosclerosis, focal | Glomerular disease characterised by focal and segmental areas of glomerular sclerosis, usually commencing in the juxtamedullary glomeruli and gradually spreading to involve other parts of the kidney, with eventual kidney failure. (12 Dec 1998) |
| chronic focal sclerosing osteomyelitis | A reaction of bone to a mild bacterial infection, often the result of a carious tooth, in persons with a high degree of tissue resistance; results in a localised radio-opacity. Synonym: focal condensing osteitis. (05 Mar 2000) |
| plane, focal | <microscopy> A plane through the focal point perpendicular to the principle axis of a lens or mirror. (05 Aug 1998) |
| positive focal length | <microscopy> Any lens which converges parallel rays to a focus at the back of the lens is a positive lens and has a positive focal length. The focal length is measured from the second principal point of the lens to the point on the lens axis where the rays from an infinitely distant point are brought to focus. See: negative focal length. (05 Aug 1998) |
| posterior focal point | The point of a compound optical system where parallel rays entering the system are focused. (05 Mar 2000) |
| cutaneous focal mucinosis | Flesh-coloured papules of the skin, composed of homogenous mucinous material with scattered fibroblasts. (05 Mar 2000) |
| proximal femoral focal deficiency | A congenital defect in which variable portions of the upper end of the femur are reduced or absent. (05 Mar 2000) |
| negative focal length | <physics> The focal length of a negative lens. Parallel rays impinging on a negative lens can be traced to a virtual focus which exists on the same side of the lens as the impinging rays. The distance from the second principal point of the lens to this second focal point is measured on the same side of the lens as is the object. See: negative lens, focal length. (05 Aug 1998) |
| dystonia, focal, due to blepharospasm | The second most common focal dystonia, the involuntary, forcible closure of the eyelids. The first symptoms may be uncontrollable blinking. Only one eye may be affected initially, but eventually both eyes are usually involved. The spasms may leave the eyelids completely closed causing functional blindness even though the eyes and vision are normal. (12 Dec 1998) |